The utilization of MGMT promoter methylation testing in United States hospitals for glioblastoma and its impact on prognosis.

Multiple studies have identified O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation status to be an important prognostic factor in glioblastoma (GBM). We used the National Cancer Data Base (NCDB) to analyze completeness of coding for MGMT as well as to compare outcomes of GBM patients treated with adjuvant chemoradiation based on MGMT promoter methylation status (positive, negative, unknown). Patients diagnosed with GBM from 2010 to 2012 who received adjuvant chemoradiation were identified. MGMT promoter methylation status was obtained. The Kaplan-Meier method was used to assess overall survival (OS) by coding status of MGMT promoter methylation (positive, negative, unknown) and Cox regression analysis was used to assess impact of covariables on OS. There were 12,725 patients who met the study criteria, of which 626 (4.9%) were MGMT+, 1,037 (8.1%) were MGMT- and 11.062 (86.9%) were coded as unknown/not coded. Treatment at academic centers was strongly associated with MGMT promoter status testing (OR 2.23, p < 0.001), as well as hospital facility within the Northeast (OR 1.55, p < 0.001). The median and 2-year OS was 20 months and 40.2% for MGMT+ compared to 15 months and 24.1% for MGMT-, respectively (p < 0.001). For those coded as MGMT unknown, median and 2-year OS was 14.6 months and 27.5%, which was significantly worse compared to MGMT+ (p < 0.001) but not compared to MGMT- (p = 0.78). On multivariable analysis, MGMT+ was strongly associated with improved OS (HR 0.74, p < 0.001). Despite convincing evidence that MGMT promoter methylation status has a strong influence on prognosis; it appears to be a highly underutilized test in United States hospitals.